The invention relates to a medical instrument consisting of a relatively rigid shaft and a flexible tip, which is attached to one end of the shaft as an extension thereof and at whose outer end a tension cable can be fastened, that is guided essentially parallel to the tip and the shaft to its other end in a tubular sheath, and at the other end of the shaft is joined to an actuation element that allows a shortening of the tension cable so as to impart to the tip a selectable curvature in the direction of the shortened tension cable, and that the shaft and the tip consist of extruded plastic parts that are joined to one another at the transition from the shaft to the tip.
A catheter of this type has been disclosed by DE-OS 14 91 697.
Medical instruments of this kind are known, in the form of "controllable tip" endoscopes. The shaft consists of a relatively rigid metal or plastic tube, the interior of which, in larger-diameter endoscopes, is arranged as an instrument conduit, irrigation conduit, and the like; while thinner endoscopes, in the interest of particular miniaturization of their cross section, no longer have an actual lumen, but simply have a bundle of optical fibers passing through. The flexible tip of such endoscopes consists of a number of elements located one after the other and connected in an articulated manner to one another. Usually the cables of two Bowden wires are fastened, at two points opposite each other, to the element forming the outer end of the tip, and the sheaths of these cables are applied to the outer sides of the tip and the shaft and, in particular, are connected by means of a sheath surrounding the flexible tip and the shaft as well as the Bowden wires. Occasionally only one Bowden wire is used when it is possible to forego the ability to also re-extend the tip using Bowden wires. The curved tip can also be oriented by rotating the instrument about its longitudinal axis. In every case, the configuration of the known medical instruments which have a controllable tip at one end is relatively complex and requires a cross section of substantial size, which makes such an instrument unsuitable for many applications.
Operating methods in which relatively thin medical instruments are inserted into natural or artificial body conduits are becoming increasingly important. In such operations a controllable tip makes it possible to insert the instrument specifically into branching orifices or into those which, in the vicinity of body cavities, continue at an offset. Medical instruments with a precisely controllable tip are therefore suitable for many applications, and not only offer the operator new possibilities, but also guarantee gentler treatment of the patient.